1. Field of the Invention
The present disclosure relates to an intake manifold.
2. Discussion of the Background
In a typical automotive multi-cylinder engine, an intake manifold is fastened to the intake port side wall surface of a cylinder head, and fresh air (air or air-fuel mixture) is supplied through this intake manifold to the combustion chamber of each cylinder. Some intake manifolds include an intake air chamber in which fresh air passing through an air cleaner and a throttle body is temporarily stored, and branch pipes that distribute the fresh air in the intake air chamber to the intake port of each cylinder. Intake manifolds are sometimes manufactured by die casting of aluminum alloy. In recent years, intake manifolds have increasingly been manufactured by injection molding of resin in order to reduce weight, cost, and the like.
In the case of resin injection molding, it is difficult to form hollows (flow paths of fresh air) in the intake air chamber and each branch pipe, and so in many cases, pieces molded separately from thermoplastic resin are integrated by vibration welding (see Japanese Unexamined Patent Application Publication No. 2008-297960). For example, the intake manifold of Japanese Unexamined Patent Application Publication No. 2008-297960 is made by integrating first to third pieces by vibration welding. The first piece forms an intake air introducing portion, a surge tank main half, and a branch pipe main half. The second piece forms a surge tank sub-half that is welded to the surge tank main half. The third piece forms a branch pipe sub-half that is welded to the branch pipe main half, and a lid portion that covers an opening formed in the intake air introducing portion. In the case of Japanese Unexamined Patent Application Publication No. 2008-297960, the welded end face of the branch pipe main half and the welded end face of the opening in the first piece are adjacent to each other in the vibrating direction at the time of vibration welding, and are provided at the same position in a direction perpendicular to the vibrating direction. For this reason, in the third piece, the branch pipe sub-half and the lid portion are continuous with each other in the same plane.
In the case of Japanese Unexamined Patent Application Publication No. 2008-297960, since the branch pipe sub-half and the lid portion are continuous with each other in the same plane, the third piece can be a single piece despite the sliding relative to the first piece in the vibration